For the purpose of fabricating an optical component, etc., a conventional method of fabricating an optical component is known that involves exposing an optical component pattern onto a wafer and then developing the exposed optical component pattern. For example, an optical-component fabricating apparatus has, above an upper section of a wafer that is arranged on a stage, a glass mask on which an exposure pattern is formed and emits light from above the glass mask, thereby exposing the exposure pattern onto the wafer.
A method performed by such an optical-component fabricating apparatus is known that involves, when an optical component that occupies an area larger than the area exposed by one shot of light, sequentially joining exposure patterns together on a wafer. Moreover, if, in an optical-component fabricating apparatus, the position of a stage is incorrect, the position of the pattern that is exposed onto a wafer may be incorrect.
A pattern-misalignment preventing technology is known that involves detecting the amount of mismatch between a mask and a stage before exposure, then moving the stage in accordance with the detected amount of mismatch, and then exposing an exposure pattern onto the wafer. More particularly, before exposure, the optical-component fabricating apparatus detects the amount of mismatch between the mask and the stage and stores it. The optical-component fabricating apparatus then decides the position to be exposed to a shot in accordance with the stored amount of mismatch and exposes the patterns on the wafer in sequence with no gaps between them.
Another pattern-misalignment preventing technology is known that involves exposing a position-alignment mark onto a wafer that is coated with a resist and deciding the next position to be exposed to a shot in accordance with the position of the exposed position-alignment mark.
More particularly, the optical-component fabricating apparatus exposes a position-alignment mark onto a wafer that is coated with a resist. After that, to detect the position-alignment mark, the optical-component fabricating apparatus detects, by using detection light having a waveband different from that of the exposure light, the exposed position-alignment mark so that the resist is not exposed. Regarding the resist applied to the wafer, for the purpose of detecting the exposed position-alignment mark, a photosensitizer is used for which the refractive index of the detection light is clearly different from the refractive index of the exposure light.    Patent document 1: Japanese Laid-open Patent Publication No. 2003-86484    Patent document 2: Japanese Laid-open Patent Publication No. 6-204105    Patent document 3: Japanese Laid-open Patent Publication No. 10-326742    Patent document 4: Japanese Laid-open Patent Publication No. 2002-190444    Patent document 5: Japanese Laid-open Patent Publication No. 2003-305700
Because, in the abovementioned pattern-misalignment preventing technology that involves detecting the amount of misalignment before exposure, a position to be exposed to a shot is decided by using the amount of misalignment that is detected before exposure, it is impossible to correct any misalignment that occurs after the amount of misalignment is detected. If, for example, a misalignment occurs due to mechanical driving, etc., between a mask and a stage after the amount of misalignment is detected, it is impossible to join the patterns together accurately.
Moreover, the above technology using an exposed position-alignment mark has a disadvantage in that, for the purpose of detecting an exposed position-alignment mark, the type of the resist applied to a wafer is limited. For example, as a resist which is applied on a wafer for the purpose of detecting an exposed position-alignment mark, a photosensitizer that has clearly different refractive indexes is often used.
The present invention has been made to solve the above problems with the conventional technologies and it is an object of the present invention to join patterns together accurately without limiting the type of the resist used.